In terms of environmental protection or industrial waste reduction, an increasing number of industrial articles are recycled. Recycling can roughly be classified into reproductive use and reuse. For the reproductive use, respective parts of articles are sorted according to their materials, and reproduced as raw materials. On the other hand, the reuse is using some parts of articles as the same parts of newly produced articles.
As for lens-fitted photo film units, hereinafter called briefly film units, their bodies are collected after the exposed photo filmstrips are removed, and are disassembled through automatic disassembling lines. Functional parts of the disassembled film units, such as exposure units and flash units, are reused, and other plastic parts, such as front and rear covers, are reproduced as raw materials, as disclosed for example in Japanese Laid-open Patent Application No. 6-161042.
As well-known in the art, there are a variety of types of film units which are different from each other in external shape and in internal structure. So the automatic disassembling lines are installed for the respective film unit types. Collected used film units are to be sorted out according to their types, before being fed to the corresponding disassembling lines.
Since the film units have their essential components, like a photographic lens and a flash emitting portion, disposed on its front side, different types have different appearances, especially on the front sides. For this reason, conventional sorting apparatuses discriminate between the different types of film units by photographing the appearances of the film units as they are conveyed in a designated posture. Image data obtained by photographing each film unit are compared to reference image data that are prepared for the respective film unit types, so that the film unit type is discriminated depending upon the results of comparison. Such automatic sorting apparatuses are disclosed in Japanese Laid-open Patent Applications Nos. Hei 6-160048, Hei 8-282837, and 2000-142962.
However, there are those types of film units whose appearances can only be discriminated from other types either on the front sides or on the rear sides. For those film units, the above mentioned prior art sorting apparatuses cannot discriminate the types unless the film units are aligned to direct their discriminative sides toward the camera. Therefore, in order to make the sorting of the film units fully automatically, it is necessary to discriminate between the front side and the rear side of each article, and turn over some of the articles to align them into the designated posture and orientation, before feeding them to the photography station. Because of the need for the side discrimination and posture alignment, the sorting apparatuses of the prior arts are inevitably large in size, and take relatively longer processing time.
It may be possible to prepare the reference images respectively for the front and rear sides of each individual type, so as to determine the type by comparison of a photographed image of either the front side or the rear side of each article with the front side reference images and the rear side reference images. If the different type film units always had different rear side appearances, it could be possible to discriminate the type just by photographing one side of the individual film unit regardless of whether it is front or rear. However, since there are many types of film units that have substantially the same rear side appearances, it is necessary to check the front sides for discriminating between these types.
Furthermore, because the automatic sorting apparatus of the above mentioned prior arts just sorts out the film units as they are sequentially supplied to the sorting apparatus, if the collected film units are biased toward a particular type, the sorting apparatus will feed that type of film units to a corresponding disassembling line more frequently than other types. That is, the conventional sorting apparatus cannot equally feed the film units to the respective disassembling lines. Although the sorting apparatus and the disassembling lines have some buffering functions, if the flow of particular type film units from the sorting apparatus to the corresponding disassembling line exceeds so much over the processing capacity of that disassembling line that the excess of the film units on that line cannot be absorbed by the buffering function, the sorting apparatus itself must interrupt working. This lowers efficiency of the overall recycling operations.